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Tapeworm Infestation is the infection of the digestive tract by adult parasitic flatworms called cestodes or tapeworms. Live tapeworm larvae (coenuri) are sometimes ingested by consuming undercooked food. Once inside the digestive tract, a larva can grow into a very large adult tapeworm. Additionally, many tapeworm larvae cause symptoms in an intermediate host. For example, cysticercosis is a disease of humans involving larval tapeworms in the human body.
Among the most common tapeworms in humans are the pork tapeworm (T. solium), the beef tapeworm (T. saginata), the fish tapeworm (Diphyllobothrium spp.), and the dwarf tapeworm (Hymenolepis spp.). Infections involving the pork and beef tapeworms are also called taeniasis. Tapeworms of the genus Echinococcus infect and cause the most harm to intermediate hosts such as sheep and cattle. Infection with this type of tapeworm is referred to as Echinococcosis or hydatid disease. Symptoms vary widely, as do treatment options, and these issues are discussed in detail in the individual articles on each worm. With a few notable exceptions like the fish tapeworm, most cestodes that infect humans and livestock are cyclophyllids, and can be identified as such by the presence of four suckers on their scolex or head.
Although tapeworms in the intestine usually cause no symptoms, some people experience upper abdominal discomfort, diarrhea, and loss of appetite. Anemia may develop in people with the fish tapeworm. Infection is generally recognized when the infected person passes segments of proglottids in the stool (looks like white worms), especially if a segment is moving.
Rarely, worms may cause obstruction of the intestine. And very rarely, T. solium larvae can migrate to the brain causing severe headaches, seizures and other neurological problems. This condition is called neurocysticercosis. It can take years of development before the patient has those symptoms of the brain.
Ingestion of eggs
Tapeworm eggs are generally ingested through food, water or soil contaminated with human or animal (host) feces. For example, if a pig is infected with a tapeworm, it may pass eggs or segments (proglottids) of the adult tapeworm through its feces into soil. Each segment contains thousands of microscopic tapeworm eggs. These eggs can be ingested via food contaminated with the feces. Once the eggs have been ingested, they develop into larvae, which can migrate out of the intestines and form cysts in other tissues such as the lungs or liver. This type of infection is not common with beef or fish tapeworms, but can occur with the pork tapeworm — called cysticercosis — and can also occur with dog and sheep tapeworms — called echinococcosis.
Ingestion of larvae cysts in meat or muscle tissue
Tapeworm infection can also be caused by eating raw or undercooked meat from an animal or a fish that has the larval form of the tapeworm cysts in its muscle tissue. Once ingested, the larvae then develop into adult tapeworms in the intestines. Adult tapeworms can measure up to 55 feet (17 m) long and can survive as long as 25 years. Some tapeworms attach themselves to the walls of the intestine, where they cause irritation or mild inflammation, while others may pass through to the stool and exit the body. Unlike other tapeworms, the dwarf tapeworm can complete its entire life cycle — egg to larva to adult tapeworm — in one host. This is the most common tapeworm infection in the world and can be transmitted between humans. Even while being treated for certain tapeworm infections, reinfection can result from ingesting tapeworm eggs shed by the adult worm into the stool, as a result of insufficient personal hygiene.
Cases have been reported of intentional infection in the US by dieters desperate for rapid weight-loss. Importing or selling of tapeworms is illegal in the U.S. 
- Coenurosis, a parasitic infection in animals and humans caused by ingested eggs of various species of dog tapeworm
- Coenurosis in humans
- Parasitic worm (disambiguation)
- Taeniasis - by A.D.A.M., Inc.
- Tapeworm Infection - Health in Plain English (with pictures)
- Tapeworm symptoms in humans
- Taenia spp., tapeworm, causative agent of cysticercosis/taenosis: life cycle, health implications at MetaPathogen